Knife ring cutters serve for the production of chips, which will be used particularly for the production of particle board. Such a knife ring cutter has a knife ring. This in turn comprises a number of knife units. Each knife unit has a carrying block, which carries a knife and which has an abrasion surface. The abrasion surface is turned toward a rotor, which is mounted in a rotatable manner inside the knife ring. The knife ring is in turn surrounded by a housing.
Knives are subjected to a great extent to wear. They have a service life, which is calculated at only several hours. They must therefore be resharpened frequently. Earlier, the knives had to be dismantled for resharpening. In the meantime, however, devices have become known by means of which it is also possible to leave the knives in the knife ring during sharpening. For example, refer to DE 4,316,514 B1. Here, the knife ring can be taken off the cutter and inserted in a stand. It is mounted in a rotatable manner therein. In this position it encloses a sharpening unit for purposes of sharpening. The sharpening unit undertakes a translational movement parallel to the axis of the knife ring for purposes of sharpening, while the knife ring undertakes a slow rotational movement around its own axis. The grinding wheel is thus applied with its front side successively to the knives. Due to the translational movement, it migrates along the knife ring axis from a first front side to its other front side in the course of a time frame of approximately 1 to 2 hours.
Another process with a corresponding device for sharpening knives in the knife ring has also become known from DE 19 641 810 A1. This process basically operates differently. Here also, a sharpening device is provided, which can be placed precisely inside the knife ring as in the first-named device, and this executes a translational movement parallel to the knife ring axis. However, the knife ring is locked resistant to rotation during the sharpening process, and thus stands still until a knife or a group of knives is sharpened. Then the knife ring executes a limited rotational movement, corresponding to the distribution of the knives over the periphery of the knife ring.
The provision of a multiple number of knives, which are mechanically coupled together to form a knife group, is advantageous insofar as several knives can be equally sharpened with one translational motion. For example, if four grinding tools are present, then four knives can be sharpened simultaneously. After these four knives have been sharpened, the knife ring is rotated by a radian measure, so that the grinding tools are found in the positions of the next four knives.
Recently, the requirements for chip quality have increased. Chip quality depends on a number of parameters, including the preliminary state of the knife, the wood quality, but also the quality of the ground section. It has thus been shown that chip quality no longer satisfies the requirements. The confusing multiplicity of parameters always provides further impetus for speculations in order to discover disruptive influences. This has previously not proven successful to the extent necessary.